Direct patterning of polymer optical periodic nanostructures on CYTOP for visible light waveguiding

Optical waveguides and grating couplers based on polymer nanostructures are now considered as promising technologies for integrated biophotonic sensing systems. Commonly, structuration and patterning of polymers at the submicron scale requires the use of time and cost-consuming equipments such as electron beam lithography. Direct patterning of high refractive index polymer devices on CYTOP is now achievable and provides symmetric waveguides with top water-like claddings. In addition, transparency of polymers makes them suitable for operation in the visible range, being of major interest for biophotonic applications. In this paper, we report on the fabrication process of polymer submicronic single-mode waveguides on CYTOP for visible light operation. Sub-wavelength grating couplers with a pitch lower than 300 nm were fabricated to couple the input light into a 350 nm square cross-section waveguide. The whole device is imprinted in a single step using soft stamp lithography with a minimal residual layer. Finally, optical characterizations demonstrate a state-of-the-art transmission efficiency (around 1.5%) at the selected operating wavelength of 507 nm for different coupling angles in good agreement with simulations.